Study On Extraction And Characterization Of Flaxseed Protein And Loaded Lipid Soluble Small Molecule

Flaxseed protein is one of the main components of flaxseed,which can be used as high-quality plant protein to replace animal protein.However,it is mainly used for animal feed or discarded at present,resulting in a serious waste of resources.In order to provide basic research data for further utilization of flaxseed protein,it was extracted from hulled flaxseed,and its physical properties and nutritional value were preliminarily analyzed.Based on the difference between flaxseed protein and flaxseed water-soluble protein extracted by fractional extraction,this work investigated the loading performance of flaxseed water-soluble protein and flaxseed protein as wall materials for micromolecules,respectively,and using curcumin as a model.Specific research results are as follows:（1）Flaxseed protein was extracted by alkali extraction and acid precipitation after oil extraction from flaxseed kernel by mechanical pressing and organic solvent extraction.The content of crude protein was 98.86%.SDS-PAGE showed that the bands at 21 k Da and 33 k Da were the strongest,and the protein solubility showed a V shape with the change of p H.Seventeen kinds of amino acids were detected,including seven essential amino acids.The oil holding capacity of the same weight protein is more than 5 times of water holding capacity,and the protein has high emulsifying activity.The secondary structure stability of protein is general,but the thermal stability is good.The analysis of flaxseed protein showed that it contained 11 reported flaxseed derived proteins.After online enzymatic hydrolysis and comparison with the active peptide database,44 active peptides were estimated to be obtained after crude proteolytic hydrolysis.（2）Flaxseed soluble protein and curcumin complex were prepared.The loading capacity of curcumin on flaxseed soluble protein was 0.788μg/mg.The concentration of curcumin was 36200μg/L after lyophilization,and the solubility was 3291 times higher than that in aqueous solution.It was confirmed that flaxseed soluble protein had significant effect on curcumin in solubilization.With the increase of flaxseed soluble protein concentration from 0 mg/m L to 20 mg/m L,the TSI values of the composite system with the same load amount of curcumin decreased successively,and the stability was improved.Meanwhile,after illumination for 2 h,the retention rate of curcumin increased from about 20%to 90%.The compound system showed synergistic antioxidant effect on DPPH,ABTS+·and O^2-radical scavenging.The results of Fourier transform infrared（FTIR）fitting showed that curcumin significantly reduced the unstable secondary structure of curcumin（from 31.68%to 15.62%）,UV spectrum showed that the absorption peak intensity of the protein at about 208 nm gradually decreased and a significant red shift occurred.It indicated that the protein and curcumin had a strong interaction.（3）Flaxseed protein was used as emulsifier to prepare curcumin emulsion.When the concentration of flaxseed protein increased from 0%to 3%,the emulsions were E-0 to E-3,respectively.Among the freshly prepared emulsions,E-2 emulsion had the highest embedding rate of curcumin（91.43%）,and the concentration of curcumin in the emulsion was 96μg/m L,which was three times higher than E-0.Compared with the initial particle size of E-0（1.0μm）,the particle size of E-1-E-3 decreased significantly to about 0.6μm.In addition,E-1-E-3 could maintain a macroscopic stable state for more than 7 days,while the phase separation of E-0 occurred on the 7th day.Curcumin in the system had poor resistance to light decomposition,and the half-life of curcumin was only about 4 h.The inhibition efficiency of E-0 to E-3 on lipid oxidation increased from 55.2%to 78.8%after each emulsion was stored at room temperature and protected from light for 7 days.These results indicate that the use of flaxseed protein as emulsifier alone is helpful to stabilize curcumin emulsion,but the effect is not ideal.In the later stage,it can be considered to use polysaccharide and flaxseed protein to form compound emulsifier to enhance the stable embedding ability and other functional properties of the emulsion.